This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. ABSTRACT: The Resource currently has three electron microscopes for use: The JEM-4000FX ("IVEM"), the AEI EM-7 million-volt TEM ("HVEM"), and the FEI F-20 TEM. Single-particle cryo-EM work, and some tomography, is done on the F-20, most cryo-tomographic data collection is done on the JEM-4000, and most thick-plastic-section tomographic data collection is done on the HVEM. In all cases, the project is discussed beforehand with the user to insure that the specimen and microscope conditions will be appropriate for the study at hand. Assistance is also given with interpretation of results and further processing in the case of tomography, single-particle, or microanalysis applications. Advice is also given in preparing plunge-frozen specimens for rhe F-20 or JEM-4000, and in how to stain thick sections for the HVEM . Xing Meng is responsible for the F-20, David Barnard for the HVEM and Michael Marko for the JEM-4000. These individuals do the initial training for all users, both internal and external. Christian Renken has in turn done some training on the F-20, and David Mankus will take over, now that Christian Renken has left the RVBC. The F-20 has a modern user interface, and it can be set up for a relatively inexperienced microscopist to use, the only special precaution being loading of the specimen. The user will need to be taught SerialEM to collect tomographic tilt series, and will need to learn how recognize good specimens and good images for single-particle cryo-EM The JEM-4000 has a wide range of systems, including low dose semi automated tomography, EFTEM and EELS, STEM, and X ray microanalysis. For ordinary use of the microscope, only a short training period is required, but for special modes and operations extensive training is required, depending on the experience of the user. For short projects involving advanced techniques for inexperienced users, the microscope is operated by M. Marko with the user looking on. Except for experienced internal users, M. Marko sets up the microscope appropriately for each user, and changes the specimens. During HVEM training sessions, David Barnard sits with the user, and gives instructions on how to tilt the specimen, use the TV system for focusing, take pictures, etc. He is then responsible for assisting the user should any problems arise, and for changing specimens and developing negatives.